Lower Lake South (Gale Island) (DNR ID: 27-0133-02)
Sampling Location - GPS Coordinates: Surface Area: 1069 acres Max. Depth: 77 ft
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Lower Lake South (Gale Island) is located near the cities of Tonka Bay and Greenwood. Head west on Minnetonka Blvd toward Maplewood Rd, and turn left to stay on Minnetonka Blvd. Next turn right to stay on Minnetonka Blvd. Public boat launch is on the right.
Lower Lake South is on Lake Minnetonka which is a class 2B lake protected for aquatic life and recreation. Water quality information is available beginning in 1974. MCWD staff have been monitoring the site on Lower Lake South on a bi-weekly basis from the time of ice out (April) to the time of fall mixing (mid-October) since 2006.
Currently not available.
Monitoring season started in late April and ended in late October. A YSI multi-probe sonde was used to measure dissolved oxygen (DO), temperature (oC), pH, and specific conductivity (µS/cm) at each meter depth from the water surface to the bottom. Water samples were collected at one meter below the water surface and one meter from the bottom. Surface and bottom sample parameters analyzed included total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), total nitrogen (TN), total dissolved nitrogen (TDN), nitrate/nitrite (NO3/NO2) and ammonia (NH4). Surface concentrations of chlorophyll-a were also analyzed and measurements of Secchi disc depth were recorded. An additional TP sample was taken one meter below the thermocline mixing zone once stratification developed.
| 2008 Summer Water Quality Summary |
| Parameters | Range | Mean | TSI Value | Lake Grade |
| Months | June - Sept. | May - Sept. | ||
| Secchi Depth (m) | 2.8 - 4.2 | 3.6 | 42 | A |
| Surface TP (µg/L) | 11 - 24 | 15.7 | 44 | A |
| Chlorophyll-a (µg/L) | 3 - 12 | 5.3 | 47 | A |
| Overall Score | 44 | A |
The following summary refers to Figure 3.29 (a-d).
- Secchi disk depth decreased from 3.4 m to 2.3 m in the beginning of the season, and then increased to 4.2 m by late July. Secchi disk depth decreased for the remainder of the season with a slight increase in October (standard > 1.2 m).
- Chlorophyll-a concentrations for majority of the season were between 3 µg/L and 7 µg/L. In early May and late September, chlorophyll-a concentrations were greater than 10 µg/L, but did not surpass the standard (< 15 µg/L).
- Surface TP concentrations were below the standard limit for the season (< 40 µg/L) and fluctuated between 11 µg/L and 24 µg/L. Surface SRP were below detection limit (< 0.005 µg/L) except in early May.
- Both bottom TP and SRP concentrations increased over the season. In late June, bottom TP concentrations spiked to 680 µg/L, and then decreased to 84 µg/L by early July.
Lake Grades and Historical Monitoring Summaries
When available, previous reports are linked to applicable year. Additional lake data previous to 2007 may be available in the applicable year's hydrodata report. If you have additional questions or you are looking for specific information please contact MCWD's Water Quality Staff.
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